Telephone security device

ABSTRACT

In order to prevent the unauthorized use of dial-type telephones to make long distance calls, the security device of the present invention is fitted to the outer case of a standard desk or walltype telephone instrument. In position, it permits the dialing of up to, say, eight digits, and then prevents the dialing of any further digits until the telephone handpiece has been replaced and removed. The number of digits permitted will depend upon the type of installation, eight digits being used in a PABX: in a PABX a long distance direct dialed call requires the dialing of 9-1-and seven digits, i.e. nine digits in all, and any attempted call is aborted in the absence of the last digit. A lug on the rotatable dial mechanically sets a stop after eight dialings, which stop then engages the lug to prevent the ninth dialing.

United States Patent [72] Inventor Rainseford H. Ireland North Kildonan,Manitoba, Canada [21] Appl. No. 732,632

[22] Filed May 28, 1968 [45] Patented Jan. 12, 1971 [73] Assignee Johnuli er Blick [32] Priority Apr. 1, 1968 [33] Canada [54] TELEPHONESECURITY DEVICE 11 Claims, 24 Drawing Figs.

[52] U.S.C1 179/189 [51] Int. Cl H04m1/66 [50] Field of Search 179/189D,189, 179

[56] References Cited UNITED STATES PATENTS 3,358,087 12/1967 VonStein179/189(D) Assistant ExaminerThomas W. Brown Attorney-Cushman, Darby &Cushman ABSTRACT: In order to prevent the unauthorized use of dialtypetelephones to make long distance calls, the security device of thepresent invention is fitted to the outer case of a standard desk orwall-type telephone instrument. In position, it permits the dialing ofup to, say, eight digits, and then prevents the dialing of any furtherdigits until the telephone handpiece has been replaced and removed. Thenumber of digits permitted will depend upon the type of installation,eight digits being used in a PABX: in a PABX a long distance directdialed call requires the dialing of 9-1-and seven digits, i.e. ninedigits in all, and any attempted call is aborted in the absence of thelast digit. A lug on the rotatable dial mechanically sets a stop aftereight dialings, which stop then engages the lug to prevent the ninthdialing.

PATENIED JAN 1 2 i971 SHEET 1 OF 7 at 2/ JQLDMK PATENTEI] JAM 21971 SHEU2 OF 7 PATENTEU JAN 1 2 i971 SHEET 3 (1F, 7

FIGS

TELEPHONE SECURITY DEVICE This invention relates to dial-type telephonesets, in which a user can by repeated operation of the dial make use ofautomatic exchange facilities to cause his connection to anothertelephone set.

In commerce and in industry large privately owned telephoneinstallations are often used, all connected to a private branch exchange(PBX) by means of which any telephone set in the installation can beconnected to any other telephone set in the installation without makinguse of the telephone company lines external to the installation. Thusone common system is for each telephone set in the installation to beprovided with a dial by which a user can make use of automatic exchangefacilities in the PBX to connect himself automatically to any othertelephone in the installation. In many installations, connection to anoutside line must be made through an operator at the PBX, for example bydialing 0.

With the development of the size of these installations, the automaticfacilities have in many cases been extended so that a user can, by firstdialing 9, connect his telephone set to the telephone system of theexternal telephone company, and can then proceed to dial any externaltelephone number he wishes. For local calls, this is usually acceptableto the owner of the PBX, and when the system is used to make longdistance calls through the telephone operator of the external telephonecompany, the record of such calls kept by that operator for chargingpurposes usually is sufiicient to prevent any serious abuse of theability of any telephone user in the installation to make long distancecalls.

With the advent of direct distance dialing, a user of any telephone setin the installation can first dial 9 to obtain connection to theexternal telephone company equipment, can

then dial 1 to obtain automatic connection to the direct distancedialing" equipment of the external telephone company, and then canproceed to call almost any telephone number in Canada and the UnitedStates. The equipment of the external telephone company records all suchcalls for charging purposes, but only identifies the calling PBX. As aresult, the'system is open to abuse by users of the telephone sets ofthe installation, there being no record of which telephone set was usedto make the direct distance dialing call.

An object of the present invention is the provision of means by whichuse of a telephone set can be limited to the dialing of numbers havingno more than a predetermined number of digits. For example, in a PBXsystem having less than 999 internal lines, the apparatus of theinvention could be used to prevent all except a few of the telephonesets being used for the dialing of numbers having four or more digits,so that all calls external to the PBX must be routed through the PBXoperator. The sets not fitted with the apparatus could still be usednormally to use the 9 facility. As a further example, in a PBX systemwhere local calls were to be pennitted, the apparatus of the inventioncould be used to prevent the dialing of numbers having more than eightdigits. A telephone set so fitted could be used freely to call any otherinternal telephone set; it could be used to call the PBX operator (bydialing it could be used to call any local" number (by dialing 9 andthen the seven digit local number); it could be used to call the longdistance operator (by dialing 9 and then 0); but it could not be used tomake a direct dialed long distance call, which would necessitate dialingfirst 9, then 1, and then a seven figure telephone number. Any attemptedcall would be automatically aborted by the equipment of the externaltelephone company when the transmission of the last digit of the sevenfigure number had been delayed beyond their predetermined calling timelimit.

The present invention provides a security device suitable for use with adial-type telephone set having a handpiece, a cradle or the like onwhich the handpiece rests when not in use, and a rotary signalling dial,the device being adapted to restrict the use of the dial to theeffective dialing of a series of digits no greater in number than apredetermined number, comprising a base member adapted for securement toa standard telephone set, ratchet means carried by the base member andarranged to cooperate with a member affixed to the telephone set di'also that each time the dial is rotated in a clockwise direction with thehandpiece removed from the cradle or the like to dial a number, themember afiixed to the dial through the ratchet operating means moves theratchet means through a first predetermined distance, stop meansarranged when the ratchet means have been moved through a secondpredetermined distance from a reset position to prevent further dialingmovement of the telephone dial in a clockwise direction, reset meanscarried by the base member and actuatedautomatically when the telephonehandpiece is restored to its cradle or the like to return the ratchetmeans to its reset position, and guard means arranged to preventunauthorized disabling of the security device.

The invention will now be described, by way of example set of the cradletype to which the invention has been applied, I

the combination hand microphone/earphone handpiece and its connectingcord being omitted for the sake of clarity;

FIG. 2 is a perspective drawing of the upper part only of the telephoneset shown in FIG. 1, with a security cover for certain parts of theapparatus removed to expose the working of those parts;

FIG. 3 is a perspective drawing similar to FIG. 2 but showing the partsin an alternative working position;

FIG. 4 is a plan view, and FIG. 5 is a side elevation, of a securingclip shown in FIGS. 2 and 3;

FIG. 6 is a sectional side elevation taken on the line VI-Vl of FIG. 1;

FIG. 7 is a plan view and FIG. 8 is a side elevation of a base plateshown in FIGS. 2 and 3;

FIG. 9 is a plan view and FIG. 10 is a side elevation of a cancellerlever shown in FIGS. 2 and 3;

FIG. 11 is a plan view and FIG. 12 is a side elevation of a ratchetholder shown in FIGS. 2 and 3;

FIG. 13 is a plan view and FIG. 14 is a side elevation of a ratchetmember shown in FIGS. 2 and 3;

FIG. 15 is a plan view and FIG. 16 is a side elevation of a ratchetactuator disc shown in FIGS. 2 and 3;

FIG. 17 is a plan view and FIG. 18 is a side elevation of a bush shownin FIGS. 2 and 3; v

FIG. 19 is an underneath view of a security cover shown in FIG. 1;

FIG. 20 is a front elevation of a standard wall-type (or hooktype)telephone set to which the invention has been applied, the combinationhand microphone/earphone handpiece and its connecting cord being omittedfor the sake of clarity;

FIG. 21 is a front elevation of a base plate utilized in a securitydevice shown in FIG. 20;

FIG. 22 is a side elevation of a canceller lever shown in FIG.

FIG. 23 is a side elevation of an upper securing clip shown in FIG. 20;and

FIG. 24 is a plan view of a side securing clip shown in FIG. 20.

Referring first to FIGS. 1 to 19, the telephone set comprises a mouldedbody 1 provided at its upper part with upstanding horns 3 which normallyserve to locate axially and laterally a standard combination telephonemicrophone/earphone handpiece 4. In the set shown, two upstandingbuttons 5 and 7 located between the horns are normally depressed by thehandpiece, when the handpiece is not in use, and serve to operateswitches inside the body 1 to place the telephone set in readiness forreceiving incoming calls. In some telephone sets, the two buttons arereplaced by a single flat member which is mounted on an upstanding stemslidably carried by the body 1, and again arranged to operate switchesinside the body to condition the telephone set for transmission orreception. Mounted on the sloping front part 9 of the body 1 is arotatable dial 11 formed with 10 fingerholes I3 suitably clockwiserotation of the dial by a finger placed in any of the fingerholes, and areturn spring (not shown) biases the dial 11 in an anticlockwisedirection so that the dial normally assumes the position shown inFIG. 1. A peripheral scale 17 identifies each of the fingerholes, forthe convenience of the user of the telephone set. v

The preceding description of the telephone set is a description of astandard orthodox desk telephone such as is in use over the whole ofNorth America. The present invention relates to a security device whichcan be fitted to such a standard telephone set to modify its operationso that the dial 11 can be used to dial, in one effective group, only anumber of digits less than a predetermined number of digits.

The embodiment of the security device shown in FIGS. 1 to 19 includes abase plate 21 which is firmly secured to the body 1 by a clip 22 (seeplan view FIG. 4 and side elevation FIG. to which it is firmly attachedand which extends rearwardly, downwardly and then forwardly round aplatform 23 of the bodyl, being locked in place by a bolt 24 screwedinto clip 22 (see FIG. 6). As will be clear from the plan view of FIG. 7and the side elevation of FIG. 8, this base plate is provided with twoupstanding ears-25 formed with aligned holes 27 through which extends ahorizontal pivot pin 29 on which are mounted firstly a canceller lever31 (see plan view FIG. 9 and side view FIG. and secondly a ratchetholder 33 (see plan view FIG. 11 and side view FIG. 12). The relativedisposition of these two parts will be clear from FIG. 2. A small spring(not shown) biases the free end of the ratchet holder 33 downwardlytowards the base plate 21, and the canceller lever 31 is provided withtwo lugs 35 which lie under the ratchet holder 33. As a result, thisspring also holds the main part of the lever 31 up away from the body 1as shown in FIG. 2 so that the two buttons 5 and 7 can rise relativelyto the body 1 when the handpiece 4 is removed. On the other hand, if thehandpiece is replaced on top of the lever 31 (see FIG. 3), the two lugs35 will lift the ratchet holder 33 against the action of the biasingspring.

Pivotallymounted on the ratchet holder 33 by a vertical pivot pin 39 isa ratchet member 41 (see plan view FIG. 13

and front elevation FIG. 14) which is biased in an anticlockwisedirection, as viewed in plan, by a tension spring 43 acting between anarm of the member and the ratchet holder 33. Thus, unless otherwiseheld, the ratchet member will assume a position in which its continuedmovement is checked by its engagement with a stop 45 on the ratchetholder. Travel of the ratchet member 41 in the clockwise direction islimited by engagement of the ratchet member with a stop 46 on theratchet holder 33. Pivotally mounted on the base plate 21 is a pawl 47biased by a tension spring 49 into engagement with the teeth of theratchet member 41. The teeth of the ratchet member are so directed thatit can readily be'moved in a clockwise direction (viewed in plan) pastthe pawl, but the pawl normally prevents return movement. Thus theratchet member will normally be held by the spring 43 in set positionengaging the pawl 47.

Also mounted on the base plate 21 is a ratchet actuator 51 (see planview FIG. and side elevation FIG. 16) in the form of a circular discrotatably carried by a vertical pivot pin 53 and formed with anoutwardly extending lug 55. A downwardly extending peg 56 on the disc isaccommodated in an aperture 57 in the base plate 21 and is connected bya tension spring 59 to an anchor point 60 on the base plate. The peg isso located on the disc that the disc is biased in a clockwise direction(as viewed in plan) to a position where the peg engages the side of theaperture 57. Fivotally mounted on the disc of the ratchet actuator is aratchet 61 biased in a clockwise direction (as viewed in plan) by atension spring 63 acting between an anchor on the ratchet and an anchoron the disc. The shape of the tip of the ratchet 61 is such that as thedisc is moved in an anticlockwise direction by means of the lug 55, theratchet 61 engages one of the teeth of the ratchet member 41, and movesratchet member 41 through a sufficient distance for the pawl 47 to stepto engage the nexttooth of the ratchet member. During clockwise returnmovement of the disc of actuator 51, the ratchet 61 rides freely overthe subjacent teeth of the ratchet member 41.

Mounted in 4 hole of the dial 11 is a metal bush 65 (see underneath viewFIG. 17 and side elevation FIG. 18) carrying a lug 67 which liesradially outwardly of the periphery of the dial 11. This bush has aperipheral flange 69ai idthetubularpart of the bush is inserted in the 4fingerhole from underneath, the upper end of the tubular part then beingrolled'over to retain the bush in place. g

A security cover 71 is fitted over the mechanismon the base plate 21 toensure that the mechanismcannot be tampered with to enable unauthorizeddialing of numbers with more than a predetermined number of digits. Theunderneath view of FIG. 19 indicates how this generally square cover isprovided with a forward extension 73 which covers the ratchet actuator51. The cover is provided with a depending peripheral flange 75 which iscut away at 75A to permit movement of the lug 55 of the actuator and iscut away at 75B along the rear edge of the cover to permit free up anddown movement of the canceller lever 31. The cover is formed on itsunderside with two screw-threaded lugs 77 and 79 into which extend boltsextending respectively through aligned holes 81 and 83 in the base plate21. These bolts are fitted before the base plate is clamped to thetelephone handset, and are inaccessible until the base plate is againunclamped. The cover is also formed with a keyhole slot 85, theremovable key (not shown for which includes an inclined surface suchthat, as the key is turned in the slot, the part ofthe key provided withthe inclined surface engages the underside of the ratchet holder 33 tolift that holder and so disengage the pawl 47 from the teeth oftheratchet member 41.

In use of the telephone handset with the security device fitted to it,the telephone handpiece 4 will rest on the canceller lever 31 as shownin FIG. 3 (the security cover 71 being in place) so that the buttons 5and 7 are depressed and the telephone set is enabled to receive anyincoming calls, To make an outgoing call, the user lifts the handpiece4, so permitting the spring which acts on the ratchet holder 33 to drawthe holder downwards and raising the canceller lever 31 free of thebuttons 5 and 7, to enable the switches inside the telephone body 1 forthe making of a call. The user then commences to dial his desirednumber. Since the bush 65 is fitted to the 4 fingerhole 13, and sincethat is the hole nearest the actuator 51, even if the first numeral 1 isdialed the lug 67 on the bush 65 must pass the lug 55 of the ratchetactuator 51 and so cause an operative partial rotation of the disc ofthe actuator 51 in an anticlockwise direction. It will be seen that suchan action will take place as each digit is dialed, and each such actionwill by the action of the ratchet 61 on the teeth of the ratchet member61 cause the ratchet member 61 to step one tooth in a clockwisedirection. The pawl 47 will hold the ratchet member in the steppedposition. I

After the ratchet member 61 has stepped through'eight teeth, it engagesthe stop 46, so that upon a user trying to dial the ninth digit of anine-digit series, forward movement of the dial 111 will be stoppedpositively by engagement of lug67 with lug 55. Lug 55 cannot yield topermit continued movement of the dial 11, since ratchet 61 is heldimmovable by the ratchet member 61 which in turn is held against furthermovement by the stop 46.

It will be seen that a user attempting to dial 9 (to obtain connectionto the outside telephone company equipment), then 1 (to obtainconnection to the automatic direct distancedialing equipment) and then aseven-figure subscribers number, is prevented from completing the call.On the other hand, when calling the PBX operator (dial 0), or the localexchange (dial 9), or another number on the PBX (dialing three or fourdigits only), although the ratchet member 61 will be stepped, it willnot reach the stop as.

In the case of any dialed call, or an abortive attempt to use the directdistance dialing equipment, when the handpiece 4 is replaced it willdepress the canceling lever 31, the lugs 35 at the forward end of whichthen lift the ratchet holder 33 on its pivot pin 29 to raise the teethof the ratchet member 41 out of engagement with the pawl 47. The ratchetmember then returns automatically to its original position, ready forthe use of the dial to dial another number.

The key which has been mentioned above can be provided when it isdesired to enable certain members of the staff of an organization tomake use of the direct distance dialing facility without recourse to theoperator. Such a person could always dial 0, ask the operator to connecthim to the l facility, and then carry on with dialing his seven figuresubscribers number, since he would then have dialed in all only eightdigits. However, by inserting the key and turning it appropriately, hecan disable the security device by lifting the ratchet holder 33 andthus lifting the ratchet member 41 out of engagement with the pawl 49and the ratchet 61.

The security device described above has been applied to a desk-typetelephone, but obviously the device can readily be modified to suit saya wall-type or hook" telephone. In such a telephone, the two buttons 5and 7 are replaced with a pivoted cantilever arm forked to accept andhold the telephone handpiece, which hangs down from the forked arm orhook. The cantilever arm is arranged to actuate switches inside the bodyof the telephone set to prepare the set for the reception of calls andfor the making of calls.

FIG. 20 illustrates a wall-type telephone set 101 with the handpieceremoved to enable the cantilever hook 103 to be seen, the securitydevice being indicated at 105. In FIG. 21 the security device is shownin front elevation, and it will be seen that it is generally similar tothe security device described in connection with the desk-type telephoneset, and the same numerals are used to denote corresponding parts.However, the canceller lever 31 is replaced with a generally horizontalcanceller lever 131 mounted on a pivot 133 and normally biased upwardlyby a spring (not shown). At the end from the pivot, the lever 131 isforked and the two arms of the fork lie respectively one above and onebelow the hook 103. Thus the lever 131 follows the up and down movementof the hook. FIG. 22 is a side elevation of the lever 131, and it willbe seen that an intermediate part of the lever is provided with aninclined cam surface 135 which lies underneath the ratchet carrier 33.When the hook" and thus the lever 131 are in their uppermost positions,the ratchet carrier is drawn down towards the base plate 21. When thehook" and thus the lever 131 move down towards their lowermostpositions, the cam surface 135 jacks the ratchet carrier 33 away fromthe base plate 21. It will be seen that this action is basically similarto that in the embodiment of FIG. 1. As in the embodiment of FIG. 1, thebase plate is clamped to the telephone set, in this case the base platebeing provided with an upward and rearward extension 121A (see sideelevation FIG. 23) which fits over an upper part of the telephone setand a side securing bracket 141 (see plan view FIG. 24) fitting over asidewall of the telephone set.

It will be appreciated that any security device attracts the attentionof persons who willfully seek to disable it. It is important thereforethat the security device be engineered in such a way that it isdifficult if not impossible for it to be disabled without actualbreakage of parts. Thus the bush 65 must be fitted to the dial in amanner preventing its detachment. The fit of the security cover 71 tothe base plate must be such that it is not possible for the insertion ofany thin item such as a bent paper clip or other piece of wire to liftthe ratchet carrier 33. The keyhole in the security cover for thisreason is a potential source of weakness which must be guarded toprevent tampering. The use of a reasonably strong spring to hold theratchet holder 33 down towards the base plate 21 prevents disabling ofthe security device merely by inverting the telephone set, whichinversion otherwise would enable the ratchet holder by its own weight tomove the ratchet member 41 out of engagement with the pawl 47.Furthermore, the use of say a steel security cover 71 and the use ofnonmagnetic material for the ratchet holder prevents use of a small butpowerful magnet to disable the security device.

Since the object is to prevent clandestine use of the telephone handsetto make unauthorized calls, in some parts of the device it may be moreeffective to use material which will break rather than bend. Thus thecanceller lever 31 can be made of very stiff metal to prevent bending upthe arms upwards to disable the device without operating the switchbuttons 5 and 7, or it can be made of a brittle material which if sobent will break. It is difiicult if not impossible to prevent misuse ofthe telephone handset, but it is possible to make misuse impossiblewithout obvious damage to the parts.

As described above, the present invention finds a considerableapplication to telephone sets of a PBX system, but the use of theinvention is not limited to such systems. Thus in an ordinary householdhaving but the one telephone set, the security device can be applied tothe telephone set to prevent children from using the direct distancedialing system to make other than local calls. In such an installationthe parents can have key to disable the security device wheneverdesired.

Another application of the invention is to apartment houses and the likein which no PBX is provided but in which the use of the telephone is tobe restricted to the making of local calls, which are of course normallyuncharged calls.

The proportions of the ratchet member 41 will determine the number ofdigits which can be dialed before the ratchet member engages the stop46, and in the mass production of the security device it will bepossible to provide several alternative ratchet members which can beused to restrict the number of digits which can be dialed to five, orseven, or any desired number. For the limitation of the use of thetelephone set to interdepartmental use with an automatic private branchexchange, the number of permitted digits will depend upon the number oflines on the exchange.

In order to make the construction and operation of the security deviceclear, the key unlocking or disabling device has been showndiagrammatically only. When an unlocking device is provided, anoninterchangeable barrel type tumbler system lock will be provided witha suitable key, thus providing effective security against the use ofimproper keys.

I claim:

1. A security device suitable for use with a dial-type telephone sethaving a handpiece, a cradle in or on which the handpiece rests when notin use, and a rotary signalling dial, the device being adapted torestrict the use of the dial to the effective dialing of a series ofdigits no greater in number than a predetermined number, comprising:

a. a base member adapted for securement to said telephone set;

b. a member provided on said dial so as to extend from that dial;

c. ratchet means carried by said base member;

d. ratchet operating means arranged to cooperate with said memberprovided on said dial and, when actuated by that member, to move theratchet means through a first predetermined distance;

e. stop means arranged so that when the ratchet means has been movedthrough a second predetermined distance from a reset position furtherdialing movement of said dial in a clockwise direction is prevented;

f. reset means carried by the base member and actuated automaticallywhen said handpiece is restored to its cradle to return the ratchetmeans to its reset position; and

g. guard means arranged to prevent unauthorized disabling of thesecurity device.

2. A security device according to claim 1, in which:

a. the ratchet means include a toothed segment movable by the ratchetoperating means;

b. a pivotally mounted complementary pawl; and

c. the reset means is arranged to effect relative lateral movementbetween the teeth of the segment and the pawl to free the toothedsegment from the pawl for automatic return to the reset position.

outwardly 3. A security device according to claim 2, in which:

a. the pawl is pivotally mounted on the base member;

b. the toothed segment is pivotally mounted on the base member so thatit can rock bodily to produce said relative lateral movement between theteeth of the segment and the pawl; and

c. the reset means is arranged to rock the toothed segment on its pivoton the base member.

A security device according to claim 3, in which:

a. the telephone set is a desk-type set and the reset means comprises areset lever pivotally mounted on the base member;

b. said lever includes a part positioned over the cradle or switchbuttons of said desk-type telephone set; and

said lever is effective when depressed to effect the resetting of thetoothed segment.

. A security device according to claim 4, in which:

. the reset lever is separate from the pivoted toothed seg ment; and

b. the reset lever'includes lugs which are effective upon replacement ofthe handpiece to rock the toothed segment to efiect resetting.

. A security device according to claim 3, in which:

. the telephone set is a hook-type set and the reset means comprises areset lever pivotally mounted on the base member;

this reset lever includes parts, extending respectively above and belowthe hook of the telephone set; and

NUI

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c. the lever is effective when depressed to effect the c. the lug isarranged during clockwise dialing movement of the dial to engage theratchet means.

8. A security device according'to claim 1, in which the guard means isadapted to admit key means by which the security means can be disabled.3

9. A security device for use with a standard telephone set having acradle, a handpiece and manually operable means for producing telephonesignals identifying a telephone set comprising:

a. a base member adapted for attachment to said standard telephone set;

b. a member fixed to the signalling device;

c. ratchet means carried by said base member and adapted to cooperatewith the member, -;fixed to said signalling device such that each timesaid signalling device is operated in a normal manner to produce saidsignals, with said handpiece removed from said cradle, the member fixedto said signalling device operates to move the ratchet means through afirst predetermined distance;

d. stop means arranged when said ratchet means has been moved through asecond predetermined distance from a reset position to prevent furtherdialing of said signalling device;

e. reset means carried by the base member and actuated automaticallywhen said handpiece is restored to said cradle to return said ratchetmeans to its reset position.

10. A security device according to claim 9, in which said telephone isof the cradle type on which the handpiece rests when not in use and saidproducing means includes a rotary signalling dial.

11. A security device according to claim 9, in which said telephone isof wall-type with a hook on which the handpiec e rests when not in useand said producing means includes a rotary signalling dial. I t

1. A security device suitable for use with a dial-type telephone sethaving a handpiece, a cradle in or on which the handpiece rests when notin use, and a rotary signalling dial, the device being adapted torestrict the use of the dial to the effective dialing of a series ofdigits no greater in number than a predetermined number, comprising: a.a base member adapted for securement to said telephone set; b. a memberprovided on said dial so as to extend outwardly from that dial; c.ratchet means carried by said base member; d. ratchet operating meansarranged to cooperate with said member provided on said dial and, whenactuated by that member, to move the ratchet means through a firstpredetermined distance; e. stop means arranged so that when the ratchetmeans has been moved through a second predetermined distance from areset position further dialing movement of said dial in a clockwisedirection is prevented; f. reset means carried by the base member andactuated automatically when said handpiece is restored to its cradle toreturn the ratchet means to its reset position; and g. guard meansarranged to prevent unauthorized disabling of the security device.
 2. Asecurity device according to claim 1, in which: a. the ratchet meansinclude a toothed segment movable by the ratchet operating means; b. apivotally mounted complementary pawl; and c. the reset means is arrangedto effect relative lateral movement between the teeth of the segment andthe pawl to free the toothed segment from the pawl for automatic returnto the reset position.
 3. A security device according to claim 2, inwhich: a. the pawl is pivotally mounted on the base member; b. thetoothed segment is pivotally mounted on the base member so that it canrock bodily to produce said relative lateral movement between the teethof the segment and the pawl; and c. the reset means is arranged to rockthe toothed segment on its pivot on the base member.
 4. A securitydevice according to claim 3, in which: a. the telephone set is adesk-type set and the reset means comprises a reset lever pivotallymounted on the base member; b. said lever includes a part positionedover the cradle or switch buttons of said desk-type telephone set; andc. said lever is effective when depressed to effect the resetting of thetoothed segment.
 5. A security device according to claim 4, in which: a.the reset lever is separate from the pivoted toothed segment; and b. thereset lever includes lugs which are effective upon replacement of thehandpiece to rock the toothed segment to effect resetting.
 6. A securitydevice according to claim 3, in which: a. the telephone set is ahook-type set and the reset means comprises a reset lever pivotallymounted on the base member; b. this reset lever includes parts extendingrespectIvely above and below the hook of the telephone set; and c. thelever is effective when depressed to effect the resetting of the toothedsegment.
 7. A security device according to claim 1, in which: a. themember fixed to the telephone dial is in the form of a bush fittinginside one of the fingerholes of that dial; b. the bush carries a lugextending beyond the periphery of the dial; and c. the lug is arrangedduring clockwise dialing movement of the dial to engage the ratchetmeans.
 8. A security device according to claim 1, in which the guardmeans is adapted to admit key means by which the security means can bedisabled.
 9. A security device for use with a standard telephone sethaving a cradle, a handpiece and manually operable means for producingtelephone signals identifying a telephone set comprising: a. a basemember adapted for attachment to said standard telephone set; b. amember fixed to the signalling device; c. ratchet means carried by saidbase member and adapted to cooperate with the member fixed to saidsignalling device such that each time said signalling device is operatedin a normal manner to produce said signals, with said handpiece removedfrom said cradle, the member fixed to said signalling device operates tomove the ratchet means through a first predetermined distance; d. stopmeans arranged when said ratchet means has been moved through a secondpredetermined distance from a reset position to prevent further dialingof said signalling device; e. reset means carried by the base member andactuated automatically when said handpiece is restored to said cradle toreturn said ratchet means to its reset position.
 10. A security deviceaccording to claim 9, in which said telephone is of the cradle type onwhich the handpiece rests when not in use and said producing meansincludes a rotary signalling dial.
 11. A security device according toclaim 9, in which said telephone is of wall-type with a hook on whichthe handpiece rests when not in use and said producing means includes arotary signalling dial.